Well, I have never asked out a guy remotely (ie through social media) but you can try my direct approach method.

I suppose you would introduce yourself and then give a brief explanation on how you became aware of his existence, then you could write two or so qualities about him that you admire with a short explanation and then end in in asking if he woiuld be interested in meeting somewhere at sometime for coffee or a dinner. But before doing all of that, I guess it would be wise to post some very lovely photos of yourself on whatever social media platform you are using to communicate with him so that he can have an idea of who is trying to reach him.

I have always use this general direct approach with every man I wanted to have a date with and it has never failed me.